1. Field of the Invention
The present general inventive concept relates to a de-interlacing apparatus with an efficient noise reduction/removal device, and more particularly, to a de-interlacing apparatus with an efficient noise reduction/removal device capable of not only efficiently reducing/removing noise on images but also improving de-interlacing performance on images suffering from severe noise.
2. Description of the Related Art
There mainly exists a progressive scanning format and an interlaced scanning format for moving-picture scanning formats. For the purpose of better understanding, FIG. 1A shows a 30 Hz interlaced scanning (a 60 Hz field frequency) and FIG. 1B shows a 30 Hz progressive scanning.
The progressive scanning is performed with sampled image frames each of which is sampled at the same time, whereas the interlaced scanning is performed with sampled image frames each of which is sampled at a different time, and samplings are repeated on alternate lines. That is, in the interlaced scanning, each image frame is made up of two image fields in general, and the image fields sampled at different times are referred to as a top field and a bottom field, an odd field and an even field, an upper field and a lower field, a first field and a second field, or the like, respectively.
The Moving Picture Experts Group (MPEG) deals with an image as a unit of “one picture (a single view)”, and, in MPEG-2, the picture can be reconstructed to frames or fields. That is, a structure of reconstructing a picture to frames is referred to as a “Frame structure” and a structure of reconstructing a picture to fields is referred to as a “Field structure”.
Movies use the progressive scanning format which instantly takes and records scenes for views on film one by one and projects the views on the screen one at a time, view by view. On the other hand, TVs use the interlaced scanning format which divides one image frame into two fields and alternately scans the fields in order to display moving pictures effectively while using limited scan lines. In the NTSC color TV systems adopted in the United States, Japan, Korea, and so on, 30 frames each having 525 scan lines are sent per second for a view, and, in the PAL or the SECAM systems adopted in Europe and so on, 25 frames each having 625 scan lines are sent per second, so that the NTSC TVs processes 60 fields per second for a view, and the PAL or the SECOM TVs processes 50 fields per second for a view.
With not only the wide-spreading of the video display devices using the progressive scanning format, but also the increased necessity of data exchanges among the devices using different scanning formats, the need to convert the interlaced scanning format into the progressive scanning format is increasing more than ever. Such scanning format conversion is referred to as de-interlacing, and such a de-interlacing method is used for circumstances in which television signals through skywave broadcasts are converted into signals for computers to display television programs.
FIG. 2 is a view schematically showing a conventional de-interlacing apparatus. Referring to FIG. 2, the de-interlacing apparatus has a memory unit 210, an Motion Estimation/Motion Compensation (ME/MC) unit 220, a weight value calculation unit 230, a spatial axis execution unit 240, and a weight value averaging unit 250.
The memory 210 stores a current field f (k) (including added noise) and a previous field f (k−1) of an image inputted. The ME/MC unit 220 calculates motion vectors v using the current field f (k) (including the added noise) and the previous field f (k−1) that are stored in the memory 210. That is, the ME/MC unit 220 predicts motions using the fields before and after images and decides whether the motions exist. Further, the ME/MC unit 220 calculates a motion-compensated field fmc (k) using the current field f (k) (including the added noise), the previous field f (k−1), and the calculated motion vectors v.
The weight value calculation unit 230 calculates a weight value w for motion adaptation, using the current field f (k) (including the added noise) and the previous field f (k−1). The weight value calculated by the weight value calculation unit 230 is sent to the weight value averaging unit 250.
The spatial axis execution unit 240 carries out spatial axis deinterlacing using the current field f (k) (including the added noise) according to a method for executing the spatial axis deinterlacing, to thereby generate a progressive scan image fsp (k). That is, there exists the method using motion information and the method not using the motion information for the de-interlacing methods, and the spatial axis execution unit 240 carries out the de-interlacing without using motion information. Spatial axis de-interlacing methods include a line averaging method, a weighted median filtering method, an Edge-based line Averaging method, and so on.
The weight value averaging unit 250 performs the de-interlacing with time using the compensated field fmc (k) calculated by the ME/MC unit 220, the weight value w calculated by the weight value calculation unit 230, and the progressive scan image fsp (k) generated by the spatial axis execution unit 240, and generates a progressive scan image g (k) by the de-interlacing performed with time.
In the meantime, the conventional de-interlacing apparatus has a noise reduction device to reduce noise affecting a display for which the apparatus is provided. FIG. 3 shows a conventional noise reduction device. Referring to FIG. 3, the conventional noise reduction device has a memory 310, an ME/MC unit 320, a weight value calculation unit 330, and a weight value averaging unit 340.
The memory 310 stores a progressive scan image g (k−1) including a previous field f (k−1) and the current field f (k) (including the added noise) of an image inputted. The ME/MC unit 320 calculates motion vectors v using the current field f (k) (including the added noise) and the previous field f (k−1) of an image that are stored in the memory 310. That is, the ME/MC unit 320 predicts motions using the fields before and after images, and decides whether the motions exist. Further, the ME/MC unit 320 calculates a motion-compensated field fmc (k) using the previous field f (k−1) and the calculated motion vectors v.
The weight value calculation unit 330 calculates a weight value w for motion adaptation using the current field f (k) (including the added noise) and the previous field f (k−1). The weight value calculated by the weight value calculation unit 330 is sent to the weight value averaging unit 340.
The weight value averaging unit 340 reduces the noise by using the compensated field fmc (k) calculated by the ME/MC unit 320 and the weight value w calculated by the weight value calculation unit 330, and generates a noise-reduced image f′(k) with the noise reduction operations executed.
However, the conventional de-interlacing apparatus and noise reduction device as described above uses the current field f (k) including the added noise for motion predictions all the time, which leads to a high possibility of miscalculating motion vectors v due to the influence of the noise. Accordingly, there exists a problem in that the de-interlacing and noise reduction performance is deteriorated due to the use of miscalculated motion vectors v.